Phospholipases play essential roles in the function of alveolar macrophages and neutrophils. These enzymes release arachidonic acid from phospholipids and in that manner control the production of prostaglandins, thromboxanes and leukotrienes and other hydroxylated arachidonic acid metabolites. Phospholipases may also play an important role in the destruction of pagocytized bacteria. My preliminary results have indicated that phospholipases, particularly of the A2 type, are essential to other phagocyte functions, such as lysosomal enzyme release, independent of the release of arachidonic acid. It is the aim of this proposal to characterize the changes in phospholipid metabolism which occur in phagocytes in response to inflammatory stimuli, such as chemotactic factors, complement fragments, arachidonic acid metabolites and platelet activating factors. These changes will be characterized by HPLC and GLC analyses of lipid extracts to determine which particular acyl species of each phospholipid are involved as substrates and products of these metabolic reactions. The temporal sequence of these changes will be correlated with cellular responses such as ion fluxes, release of lysosomal enzymes and proteases, oxygen metabolism, arachidonic acid metabolism, and chemotaxis. By employing selective metabolic inhibitors of specific reactions of phospholipid metabolism and determining the effects of these inhibitors on physiological responses, essential reactions may be identified. Cells will be treated with the products of these potentially crucial reactions in an effort to determine if the products themselves are stimuli and can overcome the phospholipase inhibitors. While an understanding of phagocyte physiological responses to inflammatory stimuli is crucial to all inflammatory diseases, this project will focus on these processes in alveolar phagocytes. My findings should advance our knowledge at the molecular level of how macrophages and neutrophils are recruited into the lung and how they function in the progress of inflammatory lung diseases.